nested list comprehesion, flatten and create dict from tuple list

list.py

subland_dict = {
        'hi':['hi1','hi2','hi3'],
        'hello': ['hello1', 'hello2', 'hello3']
    }

res = [[(y,k) for y in v] for k, v in subland_dict.items()]
# [[('hi1', 'hi'), ('hi2', 'hi'), ('hi3', 'hi')], [('hello1', 'hello'), ('hello2', 'hello'), ('hello3', 'hello')]]

merged = dict(list(itertools.chain.from_iterable(res)))
# {'hi1': 'hi', 'hi2': 'hi', 'hi3': 'hi', 'hello1': 'hello', 'hello2': 'hello', 'hello3': 'hello'}